Field of the Invention
The invention relates to 1,1-diphenylethane and process for its preparation.
Discussion of the Background
1,1-Diphenylethane, also known as methyldiphenylmethane, is a familiar but economically unimportant odorant. It was described by Steffen Arctander (S. Arctander, Perfume and Flavor Chemicals, published by the Author 1969, Montclair, N.J. (USA), No. 2007.
One known synthesis of this odorant is based on the Friedel-Crafts reaction of styrene with benzene (see Spilker and Schade, Chem. Berichte, 65 (1932), 1686. The product 1,1-diphenylethane was obtained in only 25% yield. Other procedures described in the literature, for example the reaction of benzyl chloride with toluene and cupric chlorides as catalysts (U.S. Pat. No. 3,679,760) or the oxidative coupling of ethylbenzene and benzene with a catalyst consisting of aluminum and cupric chlorides (U.S. Pat. No. 3,631,211) produce only low yields and/or require costly starting materials, so that industrial use is not practical.
For economic reasons, on the other hand, procedures by which 1,1-diphenylethane might be obtained from the distillation residue of ethylbenzene production are of greater interest (see EP-A 98 677, Chem. Abstr. 73(23): 120212z and Chem. Abstr. 94 (20): 167136b.
As seen from EP-A 98 677, however, pure 1,1-diphenylethane cannot be obtained in this way since a number of impurities have very similar boiling points. Production of 1,1-diphenylethane with good fragrance quality from the distillation residue of ethylbenzene production is difficult for this reason.
Therefore, a need continues to exist for a simple and economical process for the production of 1,1-diphenylethane with good fragrance quality.